不属于加油站消防器材实行“四定”管理的是（）。
A、定养护人员
B、定期使用
C、定点摆放
D、定期换药
参考答案：B
— Where are Mr. and Mrs. Wang?
— They _____ Beijing. They _____ there twice before. [ ]
A. have been to; have gone
B. have gone to; have been
C. have been to; have gone to
D. have gone to; have been to
焊接接头组织与焊后热处理方法有什么关系？
